Electronic spotting device, applicable in particular, for the guiding of rockets and other high speed appliances



J 959 R. J. HARDY 2,892,949 ELECTRONIC SPOTTING DEVICE, APPLICABLE INPARTICULAR, FOR

THE GUIDING OF ROCKETS AND OTHER HIGH SPEED APPLIANCES 8, 1953 5Sheets-Sheet 1 Fiied Dec.

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Jun 30, 1959 R. J. HARDY 2,892,949

ELECTRONIC SPOTTING DEVICE, APPLICABLE IN PARTICULAR, FOR

THE GUIDING OF ROCKETS AND OTHER HIGH SPEED APPLIANCES Filed Dec. 8,1953 5 Sheets-Shet 2 135 157 #7 we //6 I //7 :{tx 128/ r 130 /,9/ 5 U34.-L 27 2g 2/ W: (5) 738 I82 14 I36 B (c) /i" ,l 145T (6) Mil, :0 ZambiaFiled Dec. 8, 1955 June 30, 1959 R. J. HARDY 2,892,949

ELECTRONIC SPOTTING DEVICE, APPLICABLE IN PARTICULAR, FOR THE GUIDING 0FROCKETS AND OTHER HIGH SPEED APPLIANCES 5 Sheets-Sheet 3 9 H156 156 115s H/ 52 I 8 152 200 (PM 155' v 1' z 107 ,m 157 151 is 212 225 \1 "227I 9 i U J. HARDY 2,892,949

ICULAR, FOR

June 30, 1959 R r ELECTRONIC SPOTTING DEVICE, APPLICABLE IN PART .THEGUIDING OF ROCK s, 195:5

ETS AND OTHER HIGH SPEED APPLIANCES 5 Sheets-Sheet 4 Filed Dc..

June 30, 1959 ELECTRONIC SPOTTING THE GUIDING OF ROC Filed Dec. 8. 1953HARDY R. J. DEVICE, APPLICABLE IN PARTICULAR, FOR

APPLIANCES 5 Sheets-Sheet 5 KETS'AND OTHER HIGH SPEED United. StatesPatent,

ELECTRONIC SPOTTING DEVICE, APPLICABLE IN PARTICULAR, FOR THE GUIDING 0FROCKETS AND OTHER HIGH SPEED APPLI- 'ANCES Ren J. Hardy, Paris, FranceApplication December 8, 1953, Serial No. 396,995

. Claims. priority, application FranceDecember 17,1952

6 Claims. (Cl. 250-414) The invention relates to an electronic spottingdevice which, upon receipt of radiations emitted or reflected by a fixedor mobiletarget, supplies, in the form of. signals, indications whichare a function of the coordinates of such target. These signals may alsoarise from the contrast. resulting from the shadow of the target on arelatively uniform luminous base.

This devicecan have numerous applications, such as the automatic aimingof single pieces or batteries, of artillery, and the remotecontrol, ofaerodynes moving at high speed (aircraft, rockets or missiles). However,the most interesting application of the. invention lies in the automaticguiding of such missiles, and in particular of, rockets, toward atarget.

One of:the main objects of this invention is to provide a new andimproved electronically-operating, target direction, finding apparatusmounted in a rocket or like missile, for automatically adjusting thepath of said missile to ensure impact with the target.

A further object of this invention is to provide such an apparatus withnew electronic image scanning means which will accurately andinstantaneously determine the various data (position coordinates,velocity) of a movable target.

A' still further. object of thisinvention is to provide suchscanningmeans which will limit response of the apparatus to only one target (thefirst detected target) inv the case of a plurality of targets within thefield of the apparatus.

More precisely, if for example several aircraft are in the field of the,spotting device, the. latter effects a selection and concentrates itselfon one of the aircraft, thus considerably reducing the risk ofinterference. This is obtained through. an almost instantaneousautomatic narrowing of the. field that is scanned, so that the field-islimited.-to a small zone necessary to direct the missile to thechosentarget.

The. invention will now be described in detail with reference to theaccompanying drawing, inv which:

Figure 1 shows diagrammatically an image converter as applied to theinvention,

Figure 2' is. a graph of the scanning signal and the collected, signalsin the device of Figure 1,

Figure 3 shows a collector electrode modified to form an electronamplifier,

Figure 4 illustrates a method of image analysis according to. theinvention,

Figure 5 shows av modification,

Figure 6 shows wave forms of the scanning voltages,

Figure 7 is a diagram of one embodiment of a spotting apparatus carriedout according to the invention,

Figure 8 illustrates the operation of this apparatus,

Figure 9 shows diagrammatically the assembly of an entirely electronicsearcher head constructed according to the invention,

Figure 10 shows, inthe caseof image converters, modification of thecollector electrode, and

2,892,949 Patented June 30, 1959 Figures 11 to 14 are detailed mountingdiagrams of the various parts of the assembly shown in Figure 9.

Figure 15 is a diagram of a truncated saw-tooth voltage.

Figure 1 shows an image converter I of a conventional type, such as thetube known as Farnworths image dissector; the structure and operation ofthis image dissector which is well known in the art of television, willnot be described in detail. It is sufiicient to indicate that L is anoptical lens system designed to project the optical image i of the fieldon to a screen S formed by a light-sensitive, semi-transparent,photo-cathode which converts the optical image into a correspondingstream of electrons 9 emitted by this photo-cathode. This electronicstream is accelerated and concentrated by means of a so-calledelectronic lens device E and then projected, through deflecting means,on to the bottom end 5 of the tube to form a so-called electronic image42 corresponding to the incident optical image.

This, as shown in Figure 1, on a plane 12-34, the electronic image of acertain part of space has been projected, which will hereinafter becalled simply the image.

Figure 1 also shows conventional electrostaticallyoperating deflectionelectrodes 6, 7, which enable the electronic beam 9 to be deflected soas to move the image 1234 as a whole, in translation, about an electrodehaving the form of a vertical strip 10, the axis 1415 of which occupiesa medial position in relation to the image 1- 234 when the same is atrest.

In order to make the image describe repeated move.- ments laterally inrelation to the electrode 10, of an amplitude equal to the width of suchimage, it is suflicient to apply a saw-tooth signal of the deflectingsystem 6, 7 by means of any saw-tooth pulse generator (an example ofwhich will be described hereafter). If there is a sufiicientlycontrasted target in the, field of vision of the lens system L, therewill be obtained in the plane 123-4 a spot 16 which is nothing but theelectronic image of this target. Thus, at each passage of the spot onthe electrode 10 during the entire movement of the image of the field, apulse emitted by this electrode is produced and collected at the outputcircuit 19. This signal is converted by a resistor 11 into voltage,since it produces a potential variation therethrough in accordance withOhms law, and this voltage is transmitted'through a condenser 12 to atuned circuit 17 and to the grid 13 of an amplifier valve 18.

The width of the electrode 10 must be determined with respect to thepresumed size of the spot 16 considering the mean size of the target (anaircraft, for example) and a predetermined distance, ranging about sayfrom 4000 to 5000 metres. The width of the electrode must be such thatthe signal produced is at a maximum inthe contemplated situation. Forthis purpose, this electrode should have a width equal to the diameterof the mean spot produced in such circumstances.

In addition, it is possible to obtain a sufliciently distinct separationof the signal and the background noise by adopting such a tunedfrequency for the tuned circuit 17 that the duration of the passage ofthe spot 16 on the electrode 10 should be equal to or slightly longerthan half the natural period of the circuit itself.

The saw-tooth voltage 22 (Fig. 2a) applied to the deflecting members 6,7 ensures, during its period of linear variation 2324, the movement ofthe image in front of the electrode 19 at a constant speed, whichmovement can be repeated, for example, at the rate of two hundred cyclesper second. To each scanning period 23-24 there corresponds an outputsignal consisting of a background noise 20 and a pulse 21 (Figure 2b),distinctly detached by its amplitude from such background. The part ofthis pulse 21 abovea'predetermined level 27 is used to determine (asexplained hereafter) the distance 26 to the medial axis 25, whichcorresponds with the axis 14-15 of the electrode 10. p

In the preferred application to searcher heads? or spotting apparatusfor self-guided missiles or rockets, I provide a system effecting atwofold scanning or analysis, in two perpendicular directions. The meanswhich will be described hereinafter and which allows carrying out thismethod of analysis, supplies signals corresponding to the tworectangular coordinates of the spot,'and therefore the fixing of thelatter in relation to a given origin.

1 further provide means which make it possible, when a'sp'ot such as 16is projected onto the plane 1-2-3-4, to limit the exploration orscanning of this plane to a very small zone surrounding such spot, thuseliminating all risk of interfering signals arising from nearby targetslocated within the field of vision of the system L and projected at 16'or 16".

It is obvious that instead of using an electrode member such as 16, itis possible to resort to electrodes obtained by metal plating, orobtained by masking the surface of a plate except for the part whichmust be sensitive.

In the embodiment according to Figure 3, an opening 29 has been disposedin a screen 23, arranged in such a manner that only the electronstraversing the slot 29 are able to reach a collector electrode 30disposed behind the slot. This collector electrode may be associatedwith secondary electrodes 31, 32, arranged to form with each other anelectron multiplier of known design. Thus, by means of these electrodesin series, a direct amplification is obtained, the output signal beingled from the last electrode 33, through the line 19.

Instead of an image converter, it is possible to use any other suitabletelevision camera, for example, an iconoscope, the mosaic of which, madeup of a plurality of photosensitive elementary cells, is showndiagrammatically in Figure 4. The screen 34 formed by this mosaicreceives the optical image of the visual field projected by the opticallens system and this image translates itself into a charge of thedifferent elementary cells which is proportional to the luminosity ofthe corresponding points.

In contra-distinction with television in which a very fine electronicpencil beam scans successively all the points of the image alongsuccessive lines, in the present case the electronic pencil is replacedby a far longer beam 35 extending, for example, from the top 36 to thebottom 37 of the image, but having a very slight thickness 38. Thus,when this planar beam is later-ally deflected from 39 to 40, it scansthe whole of the image.

In passing through the position 41, the beam meets the spot 16. A signal(similar to the signal 21 of Figure 2) is then produced, and makes itpossible to determine the distance 26 separating the spot 16 from themedial axis 14-15, by means of appropriate circuits, which will bedescribed hereinafter.

An analysis of the plane 34 in two perpendicular directions is necessaryin order to obtain the two rectangular coordinates of the spot 16,thereby enabling the spotting of the target aimed at.

For this purpose, different methods of analysis are pos sible. Howeverthe electron image is preferably moved in front of fixed collectorelectrodes in the manner which will be considered now.

Figure shows a cruciform electrode 65-66-67-68, in the planeperpendicular to the axis of an image converter tube similar to the oneillustrated in Figure 1 and of such a kind that the electronic imagewhich corresponds to the initial optical image on a semi-transparentphoto-cathode, forms on the plane of the electrodes.

By means of the set of electrostatic or magnetic deflecting members, acomplex signal of alternate saw-tooth p 2,892,949 'i U f; o 7' v 4 4portions is applied in order to obtain the movement of the image, firstlaterally, then vertically. The generation of such a. signal will bedescribed hereafter theoretically with reference to Figure 6 andpractically with reference to Figs. 12 and 13 (see specially tubes 318,329, 330 and 337).

At the beginning of the cycle, the left band edge of the image islocated at 72 and the centre of this image, at 73. The image moves at anuniform velocity until, for example, its centre reaches 74, then withina relatively very short time, the centre of the image passes from 74 to75, its bottom edge being at 76, the image rises more slowly and itscentre arrives at 77, and rapidly returns to the origin 73 of the cycle.

In the course of this analysis, the spot 16 first meets the electrode65-66, then, in the vertical analysis, the electrode 6768. The twopulses collected at 70, correspond to the two coordinates of the image.

During the rapid returns, only negligible pulses are produced by thepassage in front of the electrodes.

An embodiment of the invention will now be explained by taking as theanalysing device one which employs the principle set forth hereinabove,that is to say,a tube derived from conventional image converters withsemi transparent photo-cathodes, in which the electronic beam issubjected to deflecting action by means of two pairs of standarddeflecting members 60-61 and 62-63, perpendicular to each other in sucha manner that the electronic image is displaced alternately,horizontally and vertically about a cruciform fixed electrode65-66-67-68.

In accordance with the invention, a signal such as 118- 119 (Figure 69)is applied to one pair of deflecting members and a signal such as120-121 (Figure 66) to the other pair.

The signal 118-119 (or 120-121) is obtained by the superimposition of asaw-tooth signal such as 122 (Figure 6c) and of two castellated signalssuch as 123, 124 (Figure 8d) whose'amplitude 125 is half the amplitude126 of the saw-tooth signal. The castellated signal 123- 124 is appliedin phase with the saw-tooth signal 122 to a former tube (329, 330, Fig.12) for the cancellation of one serration every other time and thesecondis applied with the resultant signal obtained from the former tubeto a second tube (337, Fig. 13) for adjusting the voltage level of thecancelled serrations of the middle of the voltages of the ends of theremaining serrations. The'correspending circuit will be describedthereafter withreference to Figures 12 and 13.

In the absence of any deflection of the electron beam, the .image is atrest in the middle, with its centre at the intersection of theelectrodes 65, 66, 67, 68 (Figure 5).

Figures 7, 8 illustrate how to obtain one of the coordinates of atarget, in the form of a corresponding pulse.

The image converter I similar to one shown in Figure l is here used withan amplifier network and pulse generator 158 for the signal 21. Thisnetwork which is detailed in Figure 11, comprises an automatic gainregulator and a threshold limiter which only leads the fraction of thesignal emerging above a threshold value 27; the network then transformsthe emerging pulse into a pulse 143 of constant shape and magnitude(Fig. 8c).

The unvarying pulse 143 which has a short duration relatively to that ofthe complete scanning cycle, does not appear unless there is a detectedsignal due to a target spot on the electron image. This issuing pulse isapplied simultaneously at 130 to two mixer stages 168, 169 (detailedhereafter with reference to Figure 14) which, in the absence of a pulsedo not supply any output voltage at the terminals 181, 182.

These stages 168, 169 comprise valves with control grids which aresubstantially negatively biased and to these grids are appliedcomplementary saw-tooth signals 137, 138 issuing from the saw-toothgenerator (Figure 12), which also energizes through the line 129, thedeflecting plates 6-7 of the tube I.

As stated above, the control. grids of the mixer stages 168, 169 are ata very negative potential and when a pulse appears at 139, this pulse issuperimposed on a. valve (see 353 in Fig. 14) owing to the grid or gridsthereof on one of the complementary saw-tooth waves 137, 138. Thenegative bias of the grids is adjusted in such a manner that only duringhalf the cycle of the saw-tooth waves (the part of 137 and 138 above thecut off level 113) the invariable pulse can emerge. The magnitude 145 ofthe output signal 144 of the negatively biased values of 168, 169 willdepend on the moment at which the input pulse 143 occurs. If it occurssay just at the cut off 113 it will give no output signal, and thefarther it is from this point 115 or in other Words, the nearer it is to116 or 117, the greater will the signal 144 be.

Figure 8 illustrates the successive modifications of the signal in thecase of a spot 16 at the left of the medial axis 15 of the image e whenat rest (i.e. no deflection of the electron beam). The mixer-stage 169will be operative, since the pulse occurs when it is above cut-off, themixer-stage 168 being then below cut-ofi.

Figure 8a shows the position of the spot in this case at the distance 26from theaxis 15 and Figure 8b the resulting signal 21 which emerges fromthe network and pulse generator 158 as an unvarying square pulse 143(Figure So). In Figure 8d are shown the saw-tooth wave forms 138 and 137issuing from the saw-tooth generator 165 (the portion above cut-off 113is shown in full lines Whereas the portion below cut-off is shown indotted line). Lastly, Figure 8e shows the eventual output pulses 144issuing from the mixer-stage 169.

It will thus be seen that, according to the distance 26 of the signal 21in relation to the axis 15 of the image e, the spot 16 will eventuallygive a pulse of an amplitude 145 proportional to 26 at the terminal 182or 181 according to whether the spot is on one side or the other of theaxis 15.

The operation just described refers to only one of the coordinates ofthe target spot. In order to obtain both rectangular coordinates of thetarget, the analysis must be carried out in two perpendicular directionswith two arrangements such as the one described with reference toFigures 7 and 8. A complete device capable of providing both coordinatesis shown diagrammatically in Figure 9.

At the bottom of the image converter tube I employed, partially shown,there is a cruciform electrode 146 composed of two perpendicularbranches 65-66 and 6768. The cruciform electrode 146 is connected to theamplifier 158, with an amplification stabilised by a control circuit 159(detailed in Figure 11).

The converter tube I also comprises deflecting electrodes made up, forexample, of two pairs of standard rectangular plates 6061 and 62-63. V

This deflecting system receives two complex voltages 2013, 201, of samewave forms as those described with reference to Figure 6 in order toeffect the scanning explained with reference to this Figure, theelectronic beam 9 giving, at rest, an, image whose centre is on the axisof the cruciform electrode.

Above the deflecting system there is indicated diagrammatically at 156 apossible means of modifying the dimensions of the image, for example aconventional combination of electrodes in annular form constitutingso-called electronic lens system, in such a manner that when suitablevoltages are applied to this system, the electronic image on thecruciform analysing electrode 146 changes its dimensions, being enlargedor reduced according to the voltages applied on 156. The use of thiscomplementary device will also be described hereinafter.

The amplifier 158 allows an impulse 21 to pass, which emerges from thethreshold 27 when the analysis of the spot caused by the image of thetarget sighted traverses laterally one of the four branches of thecruciform electrode 146.

This pulse 21 controls, by means of a pulse generator (to be describedwith reference to Fig. 11) the release of an unvarying secondary pulse143 such as explained with reference to Figures 7 and 8. It is appliedsimultaneously to the control grids of valves of the four mixer-stages168, 169, 170, 171 (see Figure 14) through the connections 190, 191,192, 193.

While in the circuit of Figure 7 there were only two paths to serve,there are here four paths, only two of which can functionsimultaneously, these pairs of paths acting alternately. analysis, forexample, the paths and 171 alone can function, while the paths 168, 169will function during the vertical analysis. This result is obtainedsimply by means of a bistable oscillator or flip-flop device 162 whichfurnishes a rectangular signal synchronised by the saw-tooth generator165 (see Fig. 12). The complementary signals 163, 164 of the bi-stableoscillator are used to block alternately the two output circuits desiredand the successive pulses 143 which, alternately, relate to the verticaland horizontal analyses, are successively used in the correspondingcircuit. The complementary saw-tooth wave forms 137, 138 produced by thesaw-tooth generator including a phase splitter 165, are applied to thecontrol grids of the valves as already indicated in the description ofFigure 7.

The scanning circuit 161 produces the complex outof-phase signals 200,2111, applied to the four deflecting plates by the line 187.

The various stages and elements mentioned hereinabove are well known inthe art and an example will be given in details hereafter with referenceto Figures 11 to 14.

On the terminals 181, 182, 183, 184, there are four voltagescorresponding to the coordinates of the target, which can be used in acontrol system determining the automatic orientation of the missiletowards the target.

When a searcher head has spotted a target and is ready to direct themissile, a new target, may come within the field and give a signal ofits own, thus upsetting the steering of the missile. An object of theinvention is to provide means for reducing the field observed, so thatthe analysis is maintained only in the zone of the original target, andoperating entirely electronically to achieve this result.

In the present example, the solution consists in using the signaldetected and the impulse 143, which takes place when the target isspotted to control, by means of an integrator and a direct currentamplifier circuit 157 (see Fig. 13), the potential of the electroniclenses 156 which determine the diameter of the image formed by the beam9.

At the beginning of the spotting the field observed may be very large,with opening of 30 degrees or more, with the whole of the observed fieldconcentrated in an imageformed by the beam 9, but as soon as a target isspotted, the beam 9 becomes enlarged, so that the image is considerablyenlarged, and for this reason, the analysing cross 146 scans only partof the image, the central part, that containing the target, because thetarget spot is automatically displaced to the centre owing to thesteering action'which is determined by the target itself.

Figure 10 shows a modification of the collector electrode allowingrestriction of the field of action by means other than an electroniclens system such as 156. In this case, the control voltage issuing from157 (Figure 9) due to the presence of a spot, is applied to a series ofcom plementary pairs of electrodes 151, 152, 153, 154, ar' ranged onboth sides of the four branches of the cruciform analysing electrode146, in such a manner that when this potential is applied, the arrivalof electrons on the part opposite the cruciform electrode is prevented.But

In fact, during the lateral as these complementary electrodesdo not goas far as 'thecentre, when this potential is applied, only the centreremains active, and the analysis can be carried out only ,in the zone ofthe centre of the image, that is to say, as

if the cruciform electrode were limited in length to a very small partof its four branches disposed round the centre. At the same time, thevoltage issuing from 157 is. applied through the terminal 202 and theline 203, to. the scanning circuit, which enormously reduces theamplitude of the motion of the image, without the speed of the motion ofthe image in front of the electrodes being thereby modified, so that thetuned circuits of the ,amplifier continue to function in a suitablemanner with target is detected, the orientation of the missile becomessuch that the image of the target is carried back to the centre and apotenial applied to the complementary electrodes no longer allows thecross 146 to be sensitive except to non-deflected electrons, that is tosay, to the portion of the image comprised in the square 213, forexample.

All the circuits used and shown diagrammatically by rectangles on Figure9, are known. However, such circuits will be dealt with in detailhereinafter by way of example.

Figure 11 shows the network diagram of the amplifier 158,,thepulse-generator 160 and the control circuit 159. The cruciform electrode146 is connected to the grid of a first tuned stage 301 operating at afrequency of say 5000 cycles per second, followed by an aperiodic stage302 and by a valve 303 which only allows the passage of crests 21 of themodulation (background noise and signal) exceeding a certain level 27.This action is obtained by giving a substantial negative bias to thegrid of the valve 302 and a still more negative bias to the grid of thevalve 303. The grid resistance is made relatively large and theamplifier operates near cut-off. The valves are thus self-polarized,i.e. they do not require an external source of voltage for theirpolarisation. This selfpolarisation lowers the negative bias of the gridby an amount which increases as the background noise increases.

The modulation signal is collected on the plate of the valve 302, and itis amplified by the valve 306 which feeds a rectifier 307, supplying bythe feed-back circuit 308 the control voltage to be filtered by thetuned circuit 309, tuned to the frequency of the passage of thesuccessive lines, vertical and horizontal, of the scanning of the image.This tuned circuit 309 is designed for filtering a single frequency andmust therefore be of good quality, whereas 307 is merely an integratingcircuit for the much higher frequencies of the background noise. Thesignal separated by the threshold limiter valve 303 is used to release,at each cycle, when the pulse of the signal appears, the discharge ofthe condenser 310 (belonging to the pulse generator 160) by means of thethyratron 311. The condenser is then very rapidly recharged, to be readyfor the next cycle.

The signal thus produced which is of trapezoidal, nearly rectangularshape, is directed upon the grid of the valve 312 which constitutes amere phase splitter which supplies at 313 and 314 two invariable pulses,one positive, the other negative, whose amplitudeis obtained through thepositive and negative limitation Of the grid at the v l e 312.

The return circuits of the plates and the screen grids lead to +HT, thenegative terminal HT being the earth. The relaxation oscillatorproducing the saw-tooth voltages (circuit 165 of Figure 9) is shown onFigures 12 and 13, where 315 is a thyratron associated with a condenser316. The saw-tooth voltage issues from a potential divider 317 and feedsa class-A amplifier 318 operating as a phase splitter which supplies twosaw-teeth voltages 137 and 138 in phase opposition on the outputs 321,322. The return of the grid of the thyratron is effected at a suitablenegative polarisation for a linear form of inclination of the saw-teethand an input ter minal 323 is provided for a possible synchronisation ofthe thyratron on an outside signal.

The vertical parts of the teeth of one of the two complementarysaw-tooth wave forms act through 324 to control the bi-stable oscillatoror so-called (flip-flop) arrangement composed of two thyratrons 325,326. Such an arrangement is well known in the art. Information relatingto its operation and nature may be found in page 47 of the MassachusettsInstitute of Technology Series, volume 19 (Waveforms). The oscillatorsupplies two complementary castellated signals 163, 164, which are thenused in two mixer valves 329, 330, where they are superimposed on thesaw-tooth wave forms 137 and 138, so as to suppress alternately on eachof the outputs 331, 332, one tooth out of two, in such a manner thatthis suppression should occur alternately on one path and the other, asshown at 333, 334. One of the paths, 331 for example, will serve to feedthe vertical scanning by means of a suitable circuit, the other pathfeeding the horizontal scanning.

To produce the scanning signals, for example the vertical scanning, thesignal produced on the output 331 is led to the grid 335 of the class-Amixer-valve 337 (Figure 13) of the scanning circuit 161. This grid 335also receives the castellated signal 163 through the terminal 338connected to the terminal 339 of the flipflop 325-326 (Figure 12) whichproduces this signal.

The object of this geometrical superimposition of two simultaneoussignals is to produce the complex signal 200, already described, on theplate of the class-A mixervalve 337.

This complex signal, which is amplified and placed in phase oppositionby the two tubes 341, 342 and by a 358 on-the Figure 14 for the return346).

The mixer-stage 168 of Fig. 9 is detailed in Figure 14, which shows theuse of the detected signals, their distribution to the controls of therocket, and the pro duction of voltages for a particular correction ofthe trajectory and for the contraction of the field.

The line 350 receives the unvarying pulse 143 caused by the signal ofthe target, alternately due to the horizontal and vertical analysis ofthe field.

This line 350 is connected to the output 313 of the pulse generator ofFigure 11. The pulse 143 cannot pass indiscriminately into the fourmixer-stages 168 to 171 (see Fig. 9), because the latter are blocked oneafter the other during a quarter of a cycle owing to the castellatedvoltages 163, 164 and the saw-tooth voltages '166 and 167. During theremainder of the time, the

irate of the target One of the mixer-stages (168) is shown (in Figure14) to be connected to the inlet 190 of the unvarying pulse 143 at theline 350. The other three paths are connected to the same line at 191,192, 193.

The signal determining the degree of emergence is made up of the twocomplementary saw-tooth wave forms 137, 138 of Fig. 12, which areapplied to the lines 321 and 322 (see also Figure 8).

The circuit shown is connected at 196 and the sawtooth voltage controlsthe grid base potential, already fixed at such a value that theemergence cannot take place except in the second half of the saw-toothsignal, since the negative bias will only allow flow during half theduration of a saw-tooth signal.

Thus, if the unvarying pulse 143 coincides with the middle of thesaw-tooth, it will give no output signal Whatever, but it will give asignal if it appears in the rising part, this signal being maximum atthe peak of the saw-tooth, as explained with reference to Figure 8.

Thus, on the plate of the valve 353, a series of pulses will becollected, which can be integrated. In this way, the integrator circuit354 will supply an amplitude voltage defining the correspondingcoordinate, and this voltage can control the operation of the specialdirect current valve 355.

The valve 355, at rest, without any signal emerging on 353, has its gridat zero potential when no voltage is applied to its grid circuit 356.For this reason, the voltage at 357, could be adjusted to zero inrelation to earth, for example, by effecting the return 358 of the chain359, 360, 361, at a negative voltage, cancelling the relatively lowvoltage at 357 for a grid polarisation equal to zero, the return 362being at 250 volts, for example. But if recurrent signals are detected,the valve 355 will be negatively polarised and will for the maximumrecurrent signals attain the cutting off of the plate current, that isto say, the point 357 will be carried to about 200 volts.

More particularly, as soon as a target appears within the field of theoptical lens system, the steering means of the rocket (rudder andelevator, or spoilers) immediately react, owing to the very low timeconstant of the control circuits of the steering means, so as to bringthe target spot to the center of the image, or in other words to steerthe rocket, so that its axis is'orientated towards the. target. Howeverthis target presumably moves at a high velocity and with anapproximately rectilinear path.

Let the spot 16 (Figure 1) move, in the scanned field 1, 2, 3, 4 fromtop to bottom (say the target is an aircraft which is diving). Within avery short time, the spot 16 is returned, owing to the steering means ofthe rocket, to the centre of the cruciform electrode 146. However, asthe spot moves towards the bottom of the image, to each subsequentanalysing cycle, the correction signal such as 145 (Figure 8) has alwaysthe same direction (and the same magnitude if the target moves at auniform velocity). At the output 401 of the valve 353, voltage pulses ofsame polarity occurs at each analysing cycle. These pulses load thecondensers of the circuit 354 and therefore modify the grid bias of thevalve 355. As a consequence, the potential at 357 which was zero at thestart (image centered on the cruciform electrode), varies and apermanent direct voltage is applied, through 346, to the deflectingplate 62 (Figure 13) which deflects the whole of the image towards thetop, that is to say it tends to bring the electronic image of the targetback to the center of the cruciform electrode.

Owing to this corrective displacement of the image, the axis of themissile is no longer orientated towards the target but towards a pointlocated ahead of this target, along its path. In other words, themissile is directed, in advance, towards a position which the targetwill later reach.

Thus, in the case of targets moving transversely with v 10 respect tothe direction of the missile, it is possible to reduce or even cancelthe curvature of its path.

The voltage at 357 will be between 0 and 200 volts and will beproportional to the speed of the target. This voltage can feed one ofthe deflecting plate returns, as for example 346 of Figure 13, anddetermine the corrected centering. Complementary voltages can beapplied, originating from the inside circuits in this mixer, through theterminals of the returns 356, 363, 364, 365, the last three beingconnected to the three other paths.

The signals of the input valve 353 of the output circuit, taken in at40:1, feed the valve 402, which is connected to the integrator 403,which supplies at 181 one of the four integrated output voltagesdesigned to operate the controls of the rocket through the adequateservomotors such as rams. The terminal 182 is fed by the symmetricalpath of 181 of the vertical analysing circuit.

The negative signal 143, taken at the outlet 314 of the pulse generator160 (Figure 11) produces in the circuit 157 (Figures 9 and.13) acontinuous voltage blocking the valve 366, owing .to the integratingnetwork 405 in such a manner that when at rest, without any signal, thepotential difference at the ends of the resistor 367, which would be 100volts, for example, in the chain, rereturns to a negative voltage 368,369, 370, and falls to 10 volts when the valve 366 is blocked, owing tothe presence of a series of pulses 143 at the input 314. The eifect ofthis as shown in Fig. 15 is to truncate the signals 200, 201 applied tothe scanning output circuits 343- 341-342. In fact, when at rest, thevoltage being 100 volts on 367, the rectifiers-limiters 371 and 372 donot go into action, and do not affect the form of the signal 200 or 201of or volts applied to the phase splitter 343, while if the returnvoltage of these shunt rectifiers is reduced to +5 volts and 5 voltsrespectively (10 volts on 367), these rectifiers will cut the crests 226and 227 (Fig. 15) of the scanning signal. Thus when there is a detectedsignal, the scanning will be limited in amplitude between the levels225, but the speed of the image on the course, will remain the same.

Parallel with the voltage that limits the scanning, there will be foundon the same chain of resistances 367, 369, 370, at point, 406, a voltagewhich can be fixed by the values of the chain and the negative returnpotential 368 at zero in the absence of a signal. This potential will becarried to volts, for example, when the valve 366 is blocked by a seriesof pulses, and this voltage can be applied directly or by means of arelay valve, to the image enlarging electronic system 156 (Fig. 9), soas to reduce the portion used for analysis, or again, to create on thecomplementary electrodes 151 to 154 (Figs. 9 and 10) the absorptivevoltage preventing analysis by part of the branches of the cruciformelectrode 146.

What I claim is:

1. An electronically-operating target finding apparatus comprising anoptical system for forming an optical image of a field of investigation;means for converting said optical image into an electronic image; ananode surface opposte said electronic image and having a conductivecruciform anode with thin and rectilinear branches perpendicular to eachother; electron control means for leading the electronic beam issuedfrom said image to said anode surface in centered position with respectto the center of said cruciform anode; two pairs of deflecting membersacting on the path of said electronic beam and adapted to deflect saidbeam along two perpendicular directions parallel to said branches of thecruciform anode; a relaxation oscillator supplying a saw-tooth voltage;a phase splitter connected to said relaxation oscillator for producingtwo derived equal saw-tooth voltages in phase opposition; a flip-flopdevice synchronized by said former saw-tooth voltage and supplying twocastellated voltages in phase opposition, of same period as said derivedsaw tooth voltages and having an amplitude half of the amplitude of saidderived voltages; a.first mixer stage with two mixer valves in parallel,each having at least a control grid to which are simultaneously appliedone of said derived saw-tooth voltages and one of said castellatedvoltages, the negative part of this latter voltage bringing said mixervalve to cut-ofi whereby one of said saw-tooth out of two is eliminated;a further mixer stage with two mixer valves in parallel, each having atleast a control grid to which are simultaneously applied the outputvoltage of one valve of said mixer stage and again said cas tellatedvoltage, the level of this latter voltage being so adjusted that theoutput voltage of said valve of said further stage is during theintervals corresponding to the eliminated saw-teeth equal to the meanvalue of the sawtooth voltage; connecting means between the output ofeach of said further mixer stages and one of said pair of deflectingmeans; an amplifier the input of which is connected to said cruciformanode; a pulse generator connected to said amplifier for producing atleast a constant positive pulse when said amplifier gives a signal; twopairs of mixer stages each including a valve having at least a controlgrid, each pair being connected to said flip-flop device and to saidphase splitter for applying to the control grid of each valve the samepair one of said castellated voltages and one of said derived saw-toothvoltages; a connection between said control grid and said amplifier fortransmitting said pulses to the same; a source of negative bias for saidcontrol grid for biasing it to a voltage value equal to the mean voltageof the saw-tooth voltage plus the voltage of said pulse; and integratingnetworks connected to the output of said latter mixer stage forcollecting electrical energy of the latter.

2. An apparatus as claimed in claim 1 further comprising in the saidamplifier valves having control grids and anodes; a feed-back circuitincluding a tube with a grid and an anode and an integrating networkincluding a double rectifier connected to the anode of said tube, thegrid of said tube being connected towards the output of the saidamplifier to an anode thereof, and the output of said network towardsthe input of said amplifier to a control grid thereof.

3. An apparatus as claimed in claim 1 further comprising at the outputof the valve of each of the four latter mixer stages a rectifier; anintegrating network connected with said rectifier; a valve having acontrol grid connected with the output of said network; a potentialdivider in the anode circuit of said tube and a connection between a 12point of the said potential divider and one of the deflecting members ofa pair thereof.

4. An apparatus as claimed in claim 1 in which said pulse generatorprovides two opposed pulses and further comprising an integratingnetwork including a rectifier for receiving the negative pulses of saidopposed pulses; a valve having an anode and a control grid connected tothe output of said integrating network; a potential divider forming theanodic circuit of said valve; an electronic lens system in the electroncontrol means for varying the dimension of the electronic image withrespect to said optical image; and a connection between a point of saidpotential divider and said electronic lens system.

5. An apparatus as claimed in claim 1 in which said pulse generator,provides two opposed pulses and further comprising an integratingnetwork including a rectifier for receiving the negative pulses of saidopposed pulses; a valve having an anode anda control grid connected tothe output of said integrating network; a potential divider forming theanodic circuit of said valve; a pair of interconnected complementaryelectrodes arranged about each branch of the cruciform anode between theend of this branch and a point thereof near but spaced from the centerof said cruciform anode; and a connection between a point of saidpotential divider and said pairs of complementary interconnectedelectrodes.

6. An apparatus as claimed in claim 1 in which said pulse generatorprovides two opposed pulses and further comprising an integratingnetwork including a rectifier for receiving the negative pulses of saidopposed pulses; a valve having an anode and a control grid connected tothe output of said network; a resistance circuit for positivepolarisation of said anode; a resistor connected to said anode; tworectifiers of opposed polarities respectively connected to the ends ofsaid resistor; and a connection between the outputs of said rectifiersand the said connecting means between the output of each of said furthermixer-stages and one of said pairs of deflecting means.

References Cited in the file of this patent UNITED STATES PATENTS1,747,664 Droitcour Feb. 18, 1930 2,403,975 Graham July 16, 19462,413,870 Hammond Jan. 7, 1947 2,425,956 Salinger Aug. 19, 19472,532,063 Herbst Nov. 28, .1950

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